Lewis Structures and Lewis Dot Symbols

Electron Configurations and Valence Electrons

• Carbon has six electrons.
• The group number for an element can be used as a shortcut to determine its number of valence electrons.

Lewis Dot Symbols

• Lewis dot symbols visually represent the valence electrons of an atom.
• They are a precursor to drawing Lewis structures.

Drawing Lewis Dot Symbols

1. Determine the number of valence electrons for the atom.

2. Draw the element symbol.

3. Imagine a line on each side of the element symbol; each line can hold a maximum of two electrons.

4. Place one electron on each side before pairing them up.

   • Example: Carbon (C)
     • Carbon has four valence electrons.
     • The Lewis dot symbol for carbon is drawn with four single electrons around the C symbol.
   • Example: Nitrogen (N)
     • Nitrogen has five valence electrons.
     • The Lewis dot symbol for nitrogen is drawn with three single electrons and one lone pair around the N symbol.
   • Example: Krypton (Kr)
     • Krypton is in group eight and has eight valence electrons.
     • In its Lewis dot symbol, krypton has a full outer shell, signified by two electrons in each slot around the Kr symbol.

Lewis Structures

• Lewis structures are diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule.

Drawing Lewis Structures

1. Break apart the atoms in the molecule.

2. Connect the atoms, forming bonds.

   • Each line represents a covalent bond.

   • A covalent bond consists of two electrons being shared between two atoms.

     • Sharing valence electrons between atoms forms a covalent bond.

Covalent Bonds

• A covalent bond is formed when atoms share valence electrons to achieve a stable electron configuration.
• Each bond contains two electrons.

Example: Water (H₂O)

• The molecular formula for water is H_2O.
• The Lewis structure for water involves oxygen bonded to two hydrogen atoms.
• There are two covalent bonds: one between the oxygen and each hydrogen atom.

Lone Pair Electrons

• It is crucial to show lone pair electrons in Lewis structures.
• The presence of lone pairs indicates that a molecule can act as a base.